Human Ige Antibody Formation And The Regulatory Mechanisms Of Cell And Molecular Biology Research

IgE induction from human cells has generally been considered to be T cell dependent and to require at least two signals: IL-4 stimulation and T-B cells interaction. In the present study we report a human system of T-cell independent IgE production from highly purified B cells. When human cells were co-stimulated with an monoclonal antibody (mAb) directed against CD40 (mAb G28-5), there was induction of IgE secretion from both purified blood and tonsil B cells as well as the unfractionated lymphocytes. Anti-CD40 alone failed to induce IgE from blood mononuclear cells or purified B cells. The effect of the combination of anti-CD40 and IL-4 on IgE production was very IgE isotype specific as IgG, IgM and IgA were not increased. Furthermore, anti-CD40 with IL-5 or pokeweed mitogen (PWM) did not co-stimulate IgG, IgM or IgA and in fact strongly inhibited PWM-stimulated IgG, IgM and IgA production from blood or tonsil cells. IgE synthesis induced by anti-CD40 plus IL-4 was IFN-γ independent as is the in vivo production of IgE in humans; the doses of IFN-γ which profoundly suppressed IgE synthesis induced by IL-4 or IL-4 plus IL-6 had no inhibitory effect on anti-CD40 induced IgE production. Anti-CD23 and anti-IL-6 also could not block anti-CD40 plus IL-4 induced IgE production, but anti-IL-4 totally blocked their effect. IgE production via CD40 was not due to IL-5, IL-6 or nerve growth factor (NGF) as none of these synergized with IL-4 to induce IgE synthesis by purified B cells. Finally, we observed that CD40 stimulation alone could enhance IgE production from in vivo driven IgE producing cells from patients with very high IgE levels; cells that did not increase IgE production in response to IL-4. DL-4 plus CD40 also could induce B cells from common variable immunodeficiency (CVI) patients to produce IgE. Taken together, our data suggests that the signals delivered for IgE production by IL-4 and CD40 stimulation may mimic the pathway for IgE production seen in vivo in human allergic disease.